Calling ForgeRegistries...getValue on OreDictionary ResourceLocations return null

So if you saw my last post I fixed my recipe thingy, but I found out that

Item Ingot = ForgeRegistries.ITEMS.getValue(material.getTag());

where material.getTag() is like this (getTag() return the first par, ignore the 2nd)

DIAMOND(new ResourceLocation("forge:gems/diamond"), Type.GEM),

return null, so, how do I solve this? Is the way I'm calling this wrong? It should've crashed if it's invalid tho??